1. Field of the Invention
The present invention relates to an improved fuze initiation device to allow faster warhead detonation, and more particularly, to such a device for use in the M759 or similar stab upon impact type fuzes.
2. Background Art
The AH-64 Apache is a four-blade, twin-engine attack helicopter with a tandem cockpit for a crew of two, whose mission involves close air support to fulfill that mission; regarding which mission; the Apache is provided with an M230 chain gun with 1,200 rounds of 30 mm ammunition. The M230 Chain Gun is a single-barrel electrically operated, automatic cannon that was developed by Hughes and is currently manufactured by Alliant Techsystems. The M230 is a formidable weapon that is electrically primed, has a chamber pressure measured at 40,600 to 44,950 psi, and a muzzle velocity of 2,640 feet per second for both target practice (TP) and high-explosive dual purpose (HEDP) type ammunition. The “dual purpose” of the HEDP ammunition is its design for both anti-materiel and anti-personnel purposes. This HEDP ammunition has an aluminum cartridge, and a steel body loaded with 27 grams of PBXN-5 high explosive charge. Each HEDP round, or cartridge, or projectile, incorporates a spin compensated shaped charge liner, to help compensate for the 60,000 rpm terminal spin, and has a dual function, type M759 fuze. The fuze arms while the projectile is in flight and initiates detonation of the projectile's explosive fill upon a direct impact that causes immediate loss of velocity/momentum (i.e. dual mode action). The shaped charge liner collapses upon detonation creating an armor piercing jet with an estimated penetration performance which is in excess of 50 mm rolled homogeneous armor (RHA) at 2,500 meters. Fragmentation of the projectile body also occurs upon detonation thereby producing significant antipersonnel effects.
The current M759 fuze design incorporates as an initiation feature a generally cylindrical nylon probe with a surrounding aluminum confinement cap that moves rearward upon target impact to trigger the firing pin, i.e. point detonation (PD). This generally cylindrical nylon probe, which is located in the fuze at the nose of the 30 mm cartridge, has an integral cylindrical shoulder extending from the lower section thereof; which nylon shoulder, abuts a ledge within the aluminum o-give section of the fuze, which ledge is located toward the front of the cartridge. When the cartridge is fired, the probe is subjected to an acceleration, or setback load, of up to 100,000 g's and the subject nylon shoulder is forced, in a rearwards direction against the ledge. However, this nylon shoulder is designed to resist this setback level of force and will therefore keep the probe from moving rearward and triggering the firing pin, until the cartridge impacts a hard target and abruptly stops. Upon such a sudden stop, the force rearward imparted to the probe and its aluminum confining cup, causes the nylon shoulder to shear away against the aluminum ledge, allowing the probe to move rearwards within the fuze, thereby impacting the firing pin to initiate the detonation chain, i.e. the firing pin hits the sensitive primary explosive within the fuze (a “stabbing” type effect), which detonates and in turn ignites the secondary explosive in the body of the cartridge.
The design of the current nylon shoulder probe system is such that the nylon shoulder will not reliably shear away when the cartridge hits a soft target, such as sandy ground or plowed fields, or hits a glancing blow, where the cartridge does not immediately stop. Therefore, there is a need in the art for an initiation mechanism within the M759, or similar stab upon impact type fuzes, that will reliably allow the detonation of the cartridge upon impacting either a hard or soft target, directly or glancing. Such an initiation mechanism will afford increased lethal effect over the prior art, when utilized against soft targets in anti-personnel applications, while expending fewer cartridges.